40 . SOUTH-AFEICAX BUTTERFLIES. 



their bodies and wings began to be elongated and their flight charac- 

 teristically weakened. " It would be at this stage," writes Mr. Wallace, 

 " that some of the weaker-flying Pieridee, which happened to resemble 

 some of the Danaidas around them in their yellow and dusky tints and 

 in the general outline of their wings, would be sometimes mistaken for 

 them by the common enemy, and would thus gain an advantage in the 

 struggle for existence. Admitting this one step to be made, and all 

 the rest must inevitably follow from simple variation and survival of 

 the fittest." 



7. South-African Butterflies. 



As has been remarked above, the Extra-Tropical South-African 

 Sub-Eegion possesses representatives of all the African or Ethiopian 

 Families and Sub-Families except the Nenicohiinm, a Sub-Family of 

 Erycinidce ; but the representation of this Sub-Family in the Region 

 is exceedingly poor, only four species of one genus (Ahisara) being 

 recorded. The Butterflies known to occur in the Sub-Region and those 

 peculiar to it are numerically as follows, viz. : — 



Though the proportion of peculiar genera is thus little more than 

 one-twelfth of the entire number represented, it should be noted that 

 no fewer than twenty-one other genera — making twenty-seven in all, 

 or rather over two-fifths — are confined to the African Region. Simi- 

 larly, while but slightly above half the species appear to be endemic, 

 yet only thirteen,^ or about one-twenty-ninth, are known to extend 

 beyond the Region. 



The genera which are not known to extend into Tropical Africa are the 

 following, viz., two in the Family Nyynphalidcc (Sub-Family Satyrinm), — 

 Meneris (one species) and Ccenyra (one sj)ecies) ; and four in the Family 

 Lyccenidce, — Capys (one species), Arrugia (three species), D'Urhania 

 (three species), and Deloneura (one species). 



There are seventeen Tropical- African genera besides Ahisara, of 

 which no South- African representatives are known, viz., (Satyrince) 

 Bicydus, HeteroiJsis ; {Nymiohalinm) Imra, Elymnias, Biscoplwra, Bole- 

 schallia, Ergolis, Enotrea, Cyrestis, Aterica, and Philognoma ; ^ (Lycmn- 

 idai) Phytala, Epitola, Miletus, and Heivitsonia ; and (Hesijcridw) Cera- 

 trichia and Carystus. The rich Tropical genera Euryphene, Euphmdra^ 



^ These are Danais Chrysippus, Atella Phalantha, Pyrameis Cardid, Hypanis Ilithyia, 

 Diadema Misippus, Melanitis Leda, Yptldma Asterope, Lycmna Bxtica, L. Lysimon, L> 

 Trochihis, Terias Hecahe, Pieris Mesentina, and Teracolus Eris. 



2 Varanes, Cram,, seems properly referable to Charaxes. 



